Frequency divider



Nov. 7, 1933. w. F. CURTIS FREQUENCY DIVIDER Filed March 17, 1931 IN V EN TOR. Wm 62 (BM/4%,

A TTORNEY Patented Nov. 7, 1933 UNITED STATES PrAreuT oFFicn FREQUENCY mvnmn Westley F. Curtis, Washington, D. C.- Application March 17, 1931. Serial No. 523,373 r 5 Claims. (01. .zso-f-ssl My invention relates broadly to oscillator systems and more particularly to a circuit arrangement for effecting a .division of frequency;

One of the objects of my invention is to provide a circuit arrangement for a frequency divider by which a submultiple of a predetermined fundamental frequency may be sustained ata constant value.

Another object of my inventionis to provide a circuit arrangement for a frequency divider wherein a fundamental frequencymay be applied to the input circuit of the divider and a submultiple frequency derived from the output circuit of the frequency divider and maintained at constant frequency in synchronism with .the im pressed fundamental frequency.

Other and further objects of my invention reside in the circuitarrangement for afrequency divider as set forth more fully in the specification hereinafter following by reference to the accompanying drawing, in which:

Figure 1 diagramatically illustrates a circuit for the purpose of describing the theory of my invent-ion; Fig. 2 shows a circuit arrangement embodying my invention and employing a high frequency amplifier directly coupled with the low frequency oscillator constituting the frequency division circuitof my invention; and.Fig..3 shows an arrangementof an inductivelycoupled circuit by which connection may be made .to the low .frequency oscillator of the frequencydivision circuit.

Referring to the drawing in detail, reference character 1 designates an electron tube having cathode la, grid lb, and plate .lc with the input and output circuits coupled through the inductance 4. The grid electrode lb is connected through through condenser .2 to the terminal 3 of inductance 4. The plate electrode ,is connected throughtconductor v41 to the adjustable tap 5 on inductance 4. Atap dadiustablecalong inductance i,connectsthroughcondenser '7 with the circuit of he cathode in. Battery V8 is employed for heating the cathode ,la. .Highresistance leak path 191$ connectedvacross the grid lb and circuit of the cathode .1a. .A resonance circuit 10 .is shown constituted by inductance 1'1 and variable condenser 12 which connects to the inductance'll through theadjustable tap 42. A sliding connection 15 on inductance 11 is connected through sliding contact 16 to the inductance 4. .A resonance-circuit is providedhy the connection of vari able condenser 1% across a portion of inductance i by means of the adjustable tap 16. The high potential for the plate circuit of the oscillator system is obtained from battery 9. A coupling coil output circuit 22 of the high frequency amplifier 7.

through the right hand portion of inductance 30 v1 is coupled to inductance ll'of resonance circuit 10 andisconnected through-circuit 18120 alcohstant fr'equencyoscillator. An oscillator which is piezo electric crystal controlled may be employed'for delivering constant frequency energy through inductance 17 to the resonance circuit 10. The resonance circuit 10 is tuned by condenser 12 and adjustable-tap42 oninductance all to correspond .with the frequency of the piezoelectric crystal controlled oscillator circuit. The circuit constituted by inductance 4 and variable condenser 1 4 is adjustedto times the frequency .of the circuit-1.0. 'When the high frequency is impressed upon the circuit 10, it operates in 7 synchronism with the impressedfrequency and the circuit v4-1!l is thus controlledby the impressed frequency at a value of times ithe impressed frequency. 3. Fig. .2 shows the application of the frequency divider principle which has been illustrated in Fig. 1. YA high frequency amplifierZO constituted by anelectron tube having a cathodeZOcca grid 20?) anda plate 200 is provided with aninputcircuit 21 and an ,outputcircuit 22, the input circuit 21 being connected to theinput terminals .24. A high resistance leak path .23 .is connected across the grid electrode .20b.and the cathode 20a. .The

20 includes aresonance-circuit25. Aiconnection extends from resonance :circuit :25 through condenser 3'7 to one end of aniinductanceBO forming part of the low frequency oscillator'circuit which includes.electrontube26. The inductance has .90

ajsliding tap-connection 32 thereon ,whichis-con- .nected .to the opposite endof the resonance circuit 25. The .low frequency oscillator .26includes an inputcircuit 27 which is bridged tb yia high resistance leak path 34 andconnected through condenser 35 with one end of the inductance 30 on one side and connected to the cathode circuit on the other side. Battery 36 is providedjfor heating the cathode circuit of tubes .20 and 26. The plate circuitenergyfor both tubes 20 and,26

.is obtained from battery 29 by meansof the connection .to the mid-point v31 of inductance 30 thus completing the high potential circuit to the .plate circuit ,of tube 26 and completing 105 .the .hi h potentialcircuit for tube .20 through that portion of inductance 30 included'between center tap 31 and slidable tap' 32. The output of the frequency division circuit is shown at 33.

In lieu of the conductive connection to the low J 0 frequency oscillator from the high frequency amplifier 20 I may apply the high frequency energy prior to the frequency division operation to the circuit as illustrated in Fig. 3, where the high frequency energy is applied across terminals 40 to the inductance 39 which is inductively coupled to the inductance constituting part of the resonance circuit 25. I

As illustrated in the circuit in Fig. l, a fundamental frequency 1, equal approximately to some multiple of the frequency of the oscillator circuit is applied to the terminals 18. In Figs. 2 and 3, the resonance circuit 25 is tuned to the fundamental frequency applied at the input terminals- 24. The circuit of the low frequency oscillator including inductance 30 and condenser 37 is tuned to a sub-multiple of the fundamental frequency whereby the fundamental frequency controls the sub-multiple frequency. The energy delivered at the output terminals 38 is sustained at a sub-multiple frequency at an extremely constant value. The tuning range of the inductance 30 and condenser 37 is made sufiiciently broad to include a number of sub-multiple frequencies of a fundamental frequency which may be impressed on the low-frequency oscillator 26 from resonance circuit 25.

The operation of the circuit of my invention has been found to be markedly independent of variable battery voltages. When the frequency is controlled by an external source of high frequency, the filament voltage on both the amplifier and the oscillator may be changed by 50% without changing the frequency, or the plate voltage may be changed by 50%, or both simultaneously may be changed 25% without changing the operation of the frequency divider system. The capacity of condenser 37 must be maintained within 1% but the condenser 43 in resonant circuit 25 may change 20% without appreciable damage. The amplitude of the harmonic in circuit 25 and hence the stability of control increases with increasing coupling between the circuit 30-37 and the circuit 25. As the inductance 44 is common to the two circuits 30-37 and 25, increasing the ratio L2='C'2 and decreasing the ratio L1=C1 as well as increasing the inductive coupling between inductance 30 and inductance 44 increases the stability, where:

L1=inductance ofcoil -30. Ci capacity of condenser 37. Lz=inductance of coil 44. Cz=capacity of condenser 43.

While I have described my invention in certain preferred embodiments, I desire that it be un derstood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A frequency divider comprising an electron tube oscillator including input and output circuits, an inductance connected in common to the input and output circuits of said oscillator, a series circuit external to said inductance and extending between one end thereof and an adjustable tap along said inductance, said series circuit including 'a resonant circuit, means for impressing energy upon said resonant circuit at a frequency which is a multiple of the fundamental frequency of said oscillator and means for tuning said series circuit to a sub-multiple of said impressed frequency for deriving from said oscillator a sub-multiple of the impressed frequency.

2. A frequency divider comprising an electron tube oscillator, input and output circuits for said oscillator, an inductance connected in common to said input and output circuits for sustaining oscillations at a fundamental frequency, a circuit connected in series between separated points on said inductance for impressing energy on said inductance, at a frequency which is a multiple of the fundamental frequency of said oscillator and a tuning element connected with said output circuit for tuning said output circuit to a sub-multiple frequency of the fundamental frequency for deriving from said oscillator a sub-multiple of the impressed frequency.

3. A frequency divider comprising an electron tube oscillator, input and output circuits for said oscillator, an inductance connected in common to said input and output circuits, an auxiliary circuit comprising a resonant circuit and-a variable reactance connected in series said auxiliary circuit being connected in shunt with a portion of said inductance, said resonant circuit having energy impressed thereon at a multiple of the fundamental frequency of said oscillator, and said variable reactance being tuned to a sub-multiple of the'fundamental frequency for deriving a sub-multiple ofan impressed frequency from.

said oscillator.

4. A frequency divider comprising an electron tube oscillator, input and output circuits for said oscillator, an inductance connected in common to said input and output circuits, an auxiliary circuit connected between separated points on said inductance, said auxiliary circuit including a resonant circuit and a variable condenser in series, means for impressing energy upon said auxiliary circuit whose frequency is a multiple.

of the fundamental frequency of said oscillator, said variable condenser being tuned to a sub-multiple of the impressed frequency and a circuit connected with said output circuit for deriving a sub-multiple of the impressed frequency from said oscillator.

5. A frequency division system comprising an electron tube oscillator having input and output circuits, an inductance common to said circuits,

an amplifier circuit having a tuned output system, a source of potential for said oscillator connected with the midpoint of said inductance, a connection extending from one sideof said tuned output system of said amplifier circuit to a tap on said inductance for supplying operating potential to the output circuit of said amplifier, a

WESTLEY F. CURTIS. 

